By Anie, Clement Oliseloke
This study investigated the incidence, molecular characters and sensitivity to Buchholzia coriacea leaf extract, of methicillin-resistant Staphylococcus aureus (MRSA) nasal isolates from tertiary institution students in Delta State. Nasal swabs were collected with sterile swab sticks from nine hundred (900) apparently healthy students in the study areas and cultured on mannitol salt agar. The bacterial isolates (S. aureus) were Gram-stained, and the Gram positive isolates subjected to catalase test. The catalase - positive isolates were subjected to coagulase test and the coagulate positive isolates further subjected to DNase test for confirmation. The MRSAs were detected using oxacillin antibiotic disk (1 µg). Antimicrobial susceptibility profile of the MRSA isolates was determined according to the Clinical Laboratory Standard Institute (CLSI) Guidelines. The Kirby-Bauer method was employed to determine the susceptibility of the MRSA isolates to vancomycin. The minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of some antibiotics and the extracts were evaluated using agar dilution method. Tests were carried out to determine the presence of penicillin binding protein2a (PBP2a). The MRSA isolates were screened to determine their biofilm producing ability. Reverse Passive Latex Agglutination test was carried out to detect the presence of enterotoxins among the MRSA isolates. The methanoic and aqueous leaf extracts of Buchholzia coriacea leaf were prepared from standard protocols. Phytochemical constituents of extract and antimicrobial screening against the MRSAs were carried out according to standard methods. Molecular characterization of MRSA isolates was carried out to determine the presence of the mecA genes among the isolates. Statistical analysis was done using analysis of variance (ANOVA). Out of the nine hundred nasal samples collected from three different study locations and screened, a total of 600 (66.7%) were positive for S. aureus, based on morphology and biochemical tests. The incidence of S. aureus colonization among female and male individuals was 313(34.7%) and 287 (31.9%), respectively. There was no significant difference (p>0.05) in the females (52.2%) and males (47.8%). The antibiotic resistance pattern of the MRSA isolates was: amoxicillin > streptomycin > amoxicillin/clavulanic acid > erythromycin > chloramphenicol > co-trimoxazole > ofloxacin > ciprofloxacin > gentamicin. All the MRSA isolates had the capacity to form biofilms and produce enterotoxins, especially enterotoxin B as only one isolate produced enterotoxin C. The presence of Penicillin Binding Protein 2a was detected in the isolates tested in this study. The leaf extracts of B. coriacea contain the following: terpenes, alkaloids phenols, steroids, cardiac glycosides, anthraquinone and was found to possess antibacterial activity. Of the twenty (20) isolates of MRSA subjected to molecular characterization, only one had mecA gene. The results showed that there is presence of methicillin resistant S. aureus (MRSA) among healthy tertiary school students in Delta State of Nigeria, which are capable of producing biofilms associated with bacteria resistance. It was also observed that most of the MRSA isolates are multi-drug resistant which signifies antibiotic therapy failure in this area. It is also obvious from the results that there is the possibility of MRSA to possess penicillin binding protein 2a without mecA gene.